Amazon offers the Black + Decker 12-volt Flexi Automotive Vacuum for $31.49 with free shipping. That's the lowest price we could find by $6. It features a 12-volt cigarette lighter adapter, flexible hose, 2-in-1 flip-up brush/wide nozzle tool, long crevice tool, and 16-foot cable.

Update: The price has dropped to $31.18.